P1393

DTC P1393 G SENSOR ROUGH ROAD HIGH VOLTAGE




Circuit Description
The G sensor is a vertical low g-acceleration sensor. By sensing vertical acceleration caused by bumps or potholes in the road, the powertrain control module (PCM)/engine control module (ECM) can determine if the changes in crankshaft speed are due to engine misfire or are driveline induced. If the G sensor detects a rough road condition, the PCM/ECM misfire detection diagnostic will be de-activated. The G sensor at rest output should be between 2.35-2.65 volts (+1G). During a rough road condition, the voltage output can vary between 0.5 (-1G) and 4.5 volts (+3G).

Conditions for Setting the DTC
- The G sensor signal is greater than 4.8 volts for a total of 12.5 seconds over a 25 second period of time.

Action Taken When DTC Sets
- The Malfunction Indicator Lamp (MIL) will not illuminate.
- The PCM/ECM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records buffers.

Conditions for Clearing the MIL/DTC
- A history DTC will clear after 40 consecutive warm-up cycles without a fault.
- DTC(s) can be cleared by using the scan tool.

Diagnostic Aids
Check for the following conditions:
- Poor connection at the PCM/ECM - Inspect the harness connections for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connection.
- Damaged harness - Inspect the wiring harness for damage. If the harness appears to be OK, observe the G sensor display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the display will indicate the location of the fault.

Since the G sensor shares the PCM/ECM 5 v reference and ground terminals with Throttle Position (TP) sensor, a damaged TP harness or sensor could cause a G sensor DTC to set. See Diagnosis By Symptom.
The G sensor will give correct voltages only if it is level and mounted securely to its bracket.
Reviewing the Failure Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.

Steps 1 To 11:

Steps 12 To 13:

Test Description
The number(s) below refer to step(s) on the diagnostic table.
1. The On-Board Diagnostic (OBD II) System Check prompts the technician to complete some basic checks and store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data taken when the malfunction occurred. The information is then stored on the scan tool for later reference.